A fresh cease-fire proposal for Syria received a much-needed boost today when Iran and Turkey, two regional powers who back opposite sides in the Syrian conflict, declared their support for the plan being shopped around by United Nations special envoy to Syria Lakhdar Brahimi.

Although the actual fighting has been limited to Syria, other countries are providing funds, arms, fighters, and de facto safe havens, making outside support for the cease-fire critical to its success.

"We heard from everyone we met in the opposition, and everyone [else] we met that, if the government stops using violence, 'We will respond to this directly'," Brahimi said from Beirut today.

"The Syrian people are burying hundreds of people each day, so if they bury fewer people during the days of the holiday, this could be the start of Syria's return from the dangerous situation that it has slipped and is continuing to slip toward."

With support from Iran and Turkey secured, the next obstacle facing Brahimi is the Syrian opposition's lack of a unified leadership. The Syrian government has cited this as a key reason it has been unwilling to reach any previous agreement with the rebels, saying that even if one representative of the rebels signs an agreement, the number of factions means there is no guarantee of total buy-in from the opposition.

"The agreement has been reached, they only need to sign it now," one anonymous rebel source said. "[Foreign supporters] are telling us: 'Sort yourselves out and unite, we need a clear and credible side to provide it with quality weapons.' "

Weapons that give rebels the ability to shoot down regime aircraft could be a game-changer for a conflict in which regime forces have so far enjoyed vast military superiority, particularly because of the Air Force's ability to bomb rebel positions.

"Northern Syria is awash with advanced antitank and antiaircraft weapons. The situation has changed very quickly," a Syrian who coordinates weapons supplies from outside Syria told the Wall Street Journal.

According to rebels, the weapons, known as man-portable air defense systems (Manpads), were smuggled into the country via Turkey and Lebanon in the past two months, although Lebanon has recently cracked down on weapons smuggling and Turkey has insisted it is not involved in weapons supplying.